This invention relates to silver halide photographic light-sensitive materials having improved antistatic properties, and more particularly to photographic light-sensitive materials improved in antistatic and antiadhesion properties without adversely affecting photographic characteristics.
When photographic light-sensitive members are brought into contact with each other or the surface of a different substance, or stripped during the production or use thereof, electrostatic charges are often accumulated thereon by the contact friction or stripping, because they usually comprise an electrically insulating support and a photographic layer or layers. Such accumulated electrostatic charges give rise to various problems. Of these problems, the most serious is that the light-sensitive emulsion layer is exposed to light by discharge of the electrostatic charges accumulated before development processing, resulting in the formation of dot-like spots or tree- or feather-like line marks when photographic light-sensitive materials are developed.
These spots or line marks are called "static marks" and markedly lower the product value. In some cases, the product value is completely lost. For example, static marks appearing on medical or industrial X-ray films or the like may cause very dangerous misjudgments. The formation of such static marks is a very troublesome problem because it cannot be revealed until photographic films are developed. Furthermore, these accumulated electrostatic charges cause secondary problems, e.g., attachment of dust on the surface of photographic films and uneven coating.
The accumulation of electrostatic charges may occur during the production of the photographic light-sensitive materials or at the time of using them. For example, at production steps, the accumulation of electrostatic charges is caused by the contact friction between photographic films and rollers, or by the stripping or separation of the emulsion layer from the back side of the support during the step of winding or rewinding photographic films. At the time of using finished products, the separation of the emulsion layer from the back side of the support, for example in the case of X-ray films, due to the contact of X-ray films with mechanical parts of an automatic camera in which the X-ray film is placed or fluorescent intensifying paper is responsible for the accumulation of electrostatic charges. Additionally, the contact of X-ray films and wrapping materials causes the accumulation of electrostatic charges.
The formation of static marks on photographic light-sensitive materials which is caused by the accumulation of electrostatic charges becomes more significant with increases in the sensitivity of the photographic light-sensitive material and with increases in the processing rate thereof. Nowadays in particular, photographic light-sensitive materials are increasingly subjected to high sensitization and severe handling, e.g., high-speed coating, high-speed photographing, high-speed automatic processing, etc. This leads to easier formation of static marks.
Where an undercoating layer (sometimes referred to as a subbing layer) is provided on a film support, and a hydrophilic colloid layer, e.g., a light-sensitive silver halide emulsion layer, is provided on the undercoating layer, if electrostatic charges are accumulated on the surface of the undercoating layer, the coating of the hydrophilic colloid layer will become uneven according to the unevenness in the accumulation of electrostatic charges. This is a serious disadvantage.
The best method of removing the above-described problems is to increase the electrical conductivity so as to make accumulated electrostatic charges dissipate in a short time, before the discharge thereof.
Therefore, various methods of increasing the electrical conductivity of the support or various surface layers by incorporating therein various hygroscopic substances, water-soluble inorganic salts, surface active agents, polymers, etc., have heretofore been proposed. As such additives, polymers as described, for example, in U.S. Pat. Nos. 2 ,882,157, 2,972,535, 3,062,785, 3,262,807, 3,514,291, 3,615,531, 3,753,716 and 3,938,999, surface active agents as described, for example, in U.S. Pat. Nos. 2,982,651, 3,428,456, 3,457,076, 3,454,625, 3,552,972, and 3,655,387, and zinc oxide, semiconductors, colloid silica, etc., as described, for example, in U.S. Pat. Nos. 3,062,700, 3,245,833 and 3,525,621, are known.
Many of these substances, however, exhibit specificity, and change their effects according to the type of the support and differences in the photographic composition; that is, they provide good results when used with specific film supports and photographic emulsions, but when used with other film supports and photographic elements, they are not effective in preventing charging, and sometimes exert bad influences on photographic characteristics.
Even with such methods for increasing electrical conductivity, preventing the hydrophilic colloid layer from becoming charged is very difficult. Insufficient reduction in surface resistance at low humidities, and problems due to the contact surfaces of a photographic light-sensitive material itself, or between such material and other substances at high temperatures and humidities often take place.
On the other hand, there are some substances which are excellent in their antistatic effect, but which cannot be used because they adversely affect photographic characteristics, such as sensitivity, photographic fog, graininess, sharpness, etc., or they cause the formation of scum in a fixer. For example, although polyethylene oxide compounds are generally known to have the antistatic effect, they often exert adverse influences on photographic characteristics, such as causing an increase in fog, desensitization, reduction of graininess, etc. Additionally, copolymers of tertiary nitrogen-containing monomers and fluorine-containing monomers are effective in improving antistatic and antiadhesion properties, but their adverse influences on photographic characteristics, such as sensitivity, fog, etc., of photographic emulsions, are not improved to an extent that is completely satisfactory.
Furthermore, the antistatic ability of antistatic agents contained in photographic light-sensitive materials often deteriorates over a period of time due to the transfer and diffusion thereof during the storage of the photographic light-sensitive materials. Thus, application of antistatic agents to photographic light-sensitive materials is very difficult and the applications in which they are useful are limited.